Data transmission method and user equipment for the same

ABSTRACT

A mobile communication technology, and, more particularly, a method for efficiently transmitting data stored in a message  3  (Msg 3 ) buffer and a user equipment for the same is disclosed. The method of transmitting data by a user equipment in uplink includes receiving an uplink (UP) Grant signal from a base station on a specific message, determining whether there is data stored in a message  3  (Msg 3 ) buffer when receiving the UL Grant signal on the specific message, determining whether the specific message is a random access response message, and transmitting the data stored in the Msg 3  buffer to the base station using the UL Grant signal received on the specific message, if there is data stored in the Msg 3  buffer when receiving the UL Grant signal on the specific message and the specific message is the random access response message.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/087,988, filed on Aug. 11, 2008, which is hereby incorporated byreference as if fully set forth herein.

This application claims the benefit of Korean Patent Application No.10-2009-0057128, filed on May 21, 2009, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile communication technology, andmore particularly, to a method for efficiently transmitting data storedin a message 3 (Msg3) buffer and a user equipment for the same.

2. Discussion of the Related Art

As an example of a mobile communication system to which the presentinvention is applicable, a 3^(rd) Generation Partnership Project LongTerm Evolution (3GPP LTE) communication system will be schematicallydescribed.

FIG. 1 is a schematic view showing the network architecture of anEvolved Universal Mobile Telecommunication System (E-UMTS) as an exampleof a mobile communication system.

The E-UMTS is evolved from the existing UMTS and has been currentlystandardized in the 3GPP. Generally, the E-UMTS may be called an LTEsystem.

An E-UMTS network may be largely divided into an Evolved UMTSTerrestrial Radio Access Network (E-UTRAN) 101 and a Core Network (CN)102. The E-UTRAN 101 may include a User Equipment (UE) 103, a basestation (hereinafter, referred to as an “eNode B” or “eNB”) 104, and anAccess Gateway (AG) 105 positioned at the end of the network andconnected to an external network. The AG 105 may be divided into aportion for processing user traffic and a portion for processing controltraffic. At this time, an AG for processing new user traffic and an AGfor processing control traffic may communicate with each other using anew interface.

One or more cells may exist in one eNode B. A plurality of eNode Bs maybe connected by an interface for transmitting the user traffic orcontrol traffic. The CN 102 may include the AG 105 and a node forregistering a user of the UE 103. An interface for distinguishingbetween the E-UTRAN 101 and the CN 102 may be used.

Layers of radio interface protocol between the UE and the network may beclassified into a first layer L1, a second layer L2 and a third layer L3based on three lower layers of an Open System Interconnection (OSI)reference model that is widely known in the field of communicationsystems. A physical layer belonging to the first layer provides aninformation transfer service using a physical channel. A Radio ResourceControl (RRC) layer belonging to the third layer serves to control radioresources between the UE and the network. The UE and the networkexchange an RRC message via the RRC layer. The RRC layer may bedistributed and located at network nodes of the eNode B 104 and the AG105. Alternatively, the RRC layer may be located at only the eNode B 104or the AG 105.

FIGS. 2 and 3 show the structures of radio interface protocols betweenthe UE and the UTRAN based on a 3GPP radio access network standard.

The radio interface protocols of FIGS. 2 and 3 are horizontally formedof a physical layer, a data link layer and a network layer. The radiointerface protocols are vertically formed of a user plane fortransmitting data information and a control plane for transmittingcontrol signals. In detail, FIG. 2 shows the layers of a radio protocolcontrol plane and FIG. 3 shows the layers of a radio protocol userplane. The protocol layers of FIGS. 2 and 3 may be divided into a firstlayer (L1), a second layer (L2) and a third layer (L3) based on threelower layers of an OSI reference model that is widely known in the fieldof communication systems.

Hereinafter, the layers of the control plane of the radio protocol ofFIG. 2 and the user plane of the radio protocol of FIG. 3 will bedescribed.

A physical (PHY) layer of the first layer provides an informationtransfer service to an upper layer using a physical channel. The PHYlayer is connected to an upper layer, such as a Medium Access Control(MAC) layer, via a transport channel. Data is transferred between theMAC layer and the PHY layer via the transport channel. At this time, thetransport channel is largely divided into a dedicated transport channeland a common transport channel, depending on whether or not a channel isshared. Data is also transferred between different PHY layers, such as aphysical layer of a transmitting side and a physical layer of areceiving side, via a physical channel using radio resources.

Various layers exist in the second layer. First, the MAC layer serves tomap various logical channels to various transport channels and serves tomultiplex several logical channels into one transport channel. The MAClayer is connected to a Radio Link Control (RLC) layer, which is anupper layer, by the logical channel. The logical channel may be largelydivided into a control channel for transmitting information about thecontrol plane and a traffic channel for transmitting information aboutthe user plane according to the kinds of information transmitted.

The RLC layer of the second layer serves to segment and concatenate datareceived from an upper layer so as to adjust data size such that a lowerlayer transmits data in a radio section. In addition, the RLC providesthree modes, namely, a Transparent Mode (TM), an Unacknowledged Mode(UM) and an Acknowledged Mode (AM) in order to guarantee various Qualityof Services (QoSs) requested by Radio Bearers (RBs). In particular, theAM RLC performs a retransmission function using an Automatic Repeat andRequest (ARQ) function for reliable data transmission.

A Packet Data Convergence Protocol (PDCP) layer of the second layerperforms a header compression function to reduce the size of an InternetProtocol (IP) packet header that includes unnecessary controlinformation and has a relatively large size, for effective transmissionin a radio section having a relatively small bandwidth when transmittingan IP packet such as an IPv4 packet or an IPv6 packet. Therefore, onlynecessary information in a header portion of data is transmitted so asto improve transmission efficiency of the radio section. In the LTEsystem, the PDCP layer also performs a security function, which includesciphering for preventing data from being intercepted by a third partyand integrity protection for preventing data from being handled by athird party.

A Radio Resource Control (RRC) located at a highest portion of the thirdlayer is defined only in the control plane. The RRC layer handleslogical channels, transport channels and physical channels for theconfiguration, re-configuration and release of RBs. Here, the RBs referto logical paths provided by the first and second layers of the radioprotocol, for data transfer between the UE and the UTRAN, and theconfiguration of the RBs refers to a process of defining thecharacteristics of the radio protocol layer and channel necessary forproviding a specific service, and setting detailed parameters andoperation methods. Each of the RBs is divided into a signaling RB and adata RB. The SRB is used as a path for transmitting an RRC message inthe control plane (C-plane), and the DRB is used as a path fortransmitting user data in the user plane (U-plane).

Downlink transport channels for transmitting data from a network to a UEmay include a Broadcast Channel (BCH) for transmitting systeminformation and a downlink Shared Channel (SCH) for transmitting usertraffic or a control message. The traffic or the control message of adownlink multicast or broadcast service may be transmitted via thedownlink SCH or via a separate Downlink Multicast Channel (MCH). Uplinktransport channels for transmitting data from a UE to a network mayinclude a Random Access Channel (RACH) for transmitting an initialcontrol message and an uplink SCH for transmitting user traffic or acontrol message.

Downlink physical channels for transmitting information transferred viathe downlink transport channels in a radio section between a network anda UE may include a Physical Broadcast Channel (PBCH) for transmittinginformation about a BCH, a Physical Multicast Channel (PMCH) fortransmitting information about an MCH, a Physical Downlink SharedChannel (PDSCH) for transmitting information about a PCH and a downlinkSCH, and a Physical Downlink Control Channel (PDCCH) (also referred toas a DL L1/L2 control channel) for transmitting control informationprovided by the first layer and the second layer, such as downlink (DL)or uplink (UL) scheduling grant information. Uplink physical channelsfor transmitting information transferred via the uplink transportchannels in a radio section between a network and a UE may include aPhysical Uplink Shared Channel (PUSCH) for transmitting informationabout an uplink SCH, a Physical Random Access Channel (PRACH) fortransmitting information about an RACH, and a Physical Uplink ControlChannel (PUCCH) for transmitting control information provided by thefirst layer and the second layer, such as a HARQ ACK or NACK, aScheduling Request (SR), a Channel Quality Indicator (CQI) report.

Hereinafter, a random access procedure provided by an LTE system will beschematically described based on the above description.

First, a UE performs the random access procedure in the following cases.

when the UE performs initial access because there is no RRC Connectionwith an eNode B,

when the UE initially accesses a target cell in a handover procedure,

when the random access procedure is requested by a command of an eNodeB,

when there is uplink data transmission in a situation where uplink timesynchronization is not aligned or where a specific radio resource usedfor requesting radio resources is not allocated, and

when a recovery procedure is performed in case of radio link failure orhandover failure.

In the LTE system, there are provided two procedures in selecting arandom access preamble: one is a contention based random accessprocedure in which the UE randomly selects one preamble within aspecific group for use, and another is a non-contention based randomaccess procedure in which the UE uses a random access preamble allocatedonly to a specific UE by the eNode B. The non-contention based randomaccess procedure may be used only in the handover procedure or when itis requested by the command of the base station, as described above.

A random access procedure of a UE with a specific eNode B may largelyinclude (1) a step of, at the UE, transmitting a random access preambleto the eNode B (hereinafter, referred to as a “message 1” transmittingstep if such use will not lead to confusion), (2) a step of receiving arandom access response from the eNode B in correspondence with thetransmitted random access preamble (hereinafter, referred to as a“message 2” receiving step if such use will not lead to confusion), (3)a step of transmitting an uplink message using the information receivedby the random access response message (hereinafter, referred to as a“message 3” transmitting step if such use will not lead to confusion),and (4) a step of receiving a message corresponding to the uplinkmessage from the eNode B (hereinafter, referred to as a “message 4”receiving step if such use will not lead to confusion).

In the random access procedure, the UE stores data to be transmitted viathe message 3 in a message 3 (Msg3) buffer and transmits the data storedin the msg3 buffer in correspondence with the reception of an Uplink(UL) Grant signal. The UL Grant signal indicates information aboutuplink radio resources which may be used when the UE transmits a signalto the eNode B, and is received on a random access response messagereceived on a PDCCH or a PUSCH in the LTE system. According to thecurrent LTE system standard, it is defined that, if the UL Grant signalis received in a state in which data is stored in the Msg3 buffer, thedata stored in the Msg3 buffer is transmitted regardless of thereception mode of the UL Grant signal. As described above, if the datastored in the Msg3 buffer is transmitted in correspondence with thereception of all UL Grant signals, problems may occur. Accordingly,there is a need for research to solve such problems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a data transmissionmethod and a user equipment for the same that substantially obviate oneor more problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide a data transmissionmethod and a user equipment for the same, which is capable of solving aproblem which may occur when data stored in a message 3 (Msg3) buffer istransmitted according to a reception mode of an Uplink (UL) Grantsignal.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod of transmitting data by a user equipment through an uplinkincludes receiving an uplink grant (UL Grant) signal from a base stationon a specific message, determining whether there is data stored in amessage 3 (Msg3) buffer when receiving the UL Grant signal on thespecific message, determining whether the specific message is a randomaccess response message, and transmitting the data stored in the Msg3buffer to the base station using the UL Grant signal received on thespecific message, if there is data stored in the Msg3 buffer whenreceiving the UL Grant signal on the specific message and the specificmessage is the random access response message.

If there is no data stored in the Msg3 buffer when receiving the ULGrant signal on the specific message or the specific message is not therandom access response message, new data may be transmitted to the basestation in correspondence with the UL Grant signal received on thespecific message.

The UL Grant signal received on the specific message may be a UL Grantsignal received on a Physical Downlink Control Channel (PDCCH). In thiscase, the user equipment may transmit new data in correspondence withthe UL Grant signal received on the PDCCH.

The UL Grant signal received on the specific message may be a UL Grantsignal received on a random access response message received on PhysicalDownlink Shared Channel (PDSCH). In this case, if there is data storedin the Msg3 buffer when receiving the UL Grant signal on the randomaccess response message, the user equipment may transmit the data storedin the buffer in the Msg3 buffer using the UL Grant signal received onthe random access response message.

The data stored in the Msg3 buffer may be a Medium Access ControlProtocol Data Unit (MAC PDU) including a user equipment identifier, andthe data stored in the Msg3 buffer further include information about abuffer status report (BSR) if the user equipment starts the randomaccess procedure for the BSR.

In another aspect of the present invention, a user equipment includes areception module receiving an uplink grant (UL Grant) signal from a basestation on a specific message, a transmission module transmitting datato the base station using the UL Grant signal received on the specificmessage, a message 3 (Msg3) buffer storing UL data to be transmitted ina random access procedure, and a Hybrid Automatic Repeat Request (HARQ)entity determining whether there is data stored in the Msg3 buffer whenthe reception module receives the UL Grant signal and the specificmessage is a random access response message, acquiring the data storedin the Msg3 buffer if there is data stored in the Msg3 buffer when thereception module receives the UL Grant signal and the specific messageis the random access response message, and controlling the transmissionmodule to transmit the data stored in the Msg3 buffer to the basestation using the UL Grant signal received by the reception module onthe specific message.

The user equipment may further include a multiplexing and assemblyentity used for transmission of new data. In this case, the HARQ entitymay acquire the new data to be transmitted from the multiplexing andassembly entity if there is no data stored in the Msg3 buffer when thereception module receives the UL Grant signal on the specific message orthe received message is not the random access response message, andcontrol the transmission module to transmit the new data acquired fromthe multiplexing and assembly entity using the UL Grant signal receivedby the reception module on the specific message.

The user equipment may further include one or more HARQ processes, andHARQ buffers respectively corresponding to the one or more HARQprocesses. In this case, the HARQ entity may transfer the data acquiredfrom the multiplexing and assembly entity or the Msg3 buffer to aspecific HARQ process of the one or more HARQ processes and control thespecific HARQ process to transmit the data acquired from themultiplexing and assembly entity or the Msg3 buffer through thetransmission module.

When the specific HARQ process transmits the data stored in the Msg3buffer through the transmission module, the data stored in the Msg3buffer may be controlled to be copied into a specific HARQ buffercorresponding to the specific HARQ process, and the data copied into thespecific HARQ buffer may be controlled to be transmitted through thetransmission module.

The UL Grant signal received by the reception module on the specificmessage may be a UL Grant signal received on a Physical Downlink ControlChannel (PDCCH). In this case, the HARQ entity may control new data tobe transmitted in correspondence with the received UL Grant signalreceived on the PDCCH.

The UL Grant signal received by the reception module on the specificmessage may be a UL Grant signal received on a random access responsemessage received on Physical Downlink Shared Channel (PDSCH), and theHARQ entity may control the data stored in the Msg3 buffer to betransmitted using the UL Grant signal received on the random accessresponse message if there is data stored in the Msg3 buffer when thereception module receives the UL Grant signal on the random accessresponse message.

According to the above-described embodiments of the present invention,it is possible to transmit data stored in a Msg3 buffer according to areception mode of a UL Grant signal, without confusion.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a schematic view showing the network architecture of anEvolved Universal Mobile Telecommunication System (E-UMTS) as an exampleof a mobile communication system;

FIGS. 2 and 3 are views showing the structures of radio interfaceprotocols between a user equipment (UE) and a UMTS Terrestrial RadioAccess Network (UTRAN) based on a 3^(rd) Generation Partnership Project(3GPP) radio access network standard;

FIG. 4 is a view illustrating an operating procedure of a UE and a basestation (eNode B) in a non-contention based random access procedure;

FIG. 5 is a view illustrating an operating procedure of a UE and aneNode B in a contention based random access procedure;

FIG. 6 is a view illustrating an uplink Hybrid Automatic Repeat Request(HARQ) scheme;

FIG. 7 is a view illustrating a method of transmitting a message 3 in arandom access procedure when uplink radio resources are requested;

FIG. 8 is a view illustrating a problem which may occur when data storedin a message 3 buffer is transmitted by an Uplink (UL) Grant signalreceived on a message other than a random access response message;

FIG. 9 is a flowchart illustrating a method of transmitting uplink databy a UE according to a preferred embodiment of the present invention;

FIG. 10 is a view illustrating a method of transmitting uplink data whena Buffer status Report (BSR) is triggered in a UE, according to anembodiment of the present invention; and

FIG. 11 is a schematic view showing the configuration of a UE accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. It is to beunderstood that the detailed description which will be disclosed alongwith the accompanying drawings is intended to describe the exemplaryembodiments of the present invention, and is not intended to describe aunique embodiment which the present invention can be carried out.Hereinafter, the detailed description includes detailed matters toprovide full understanding of the present invention. However, it will beapparent to those skilled in the art that the present invention can becarried out without the detailed matters. For example, the followingdescription will be made on the assumption that a mobile communicationsystem is a 3^(rd) Generation Partnership Project Long Term Evolution(3GPP LTE) system, but the present invention is applicable to othermobile communication systems excluding the 3GPP LTE system.

In some instances, well-known structures and devices are omitted inorder to avoid obscuring the concepts of the present invention and theimportant functions of the structures and devices are shown in blockdiagram form. The same reference numbers will be used throughout thedrawings to refer to the same or like parts.

In the following description, it is assumed that a terminal includes amobile or fixed user end device such as a user equipment (UE) and amobile station (MS), and a base station includes a node of a network endcommunicating with a terminal, such as a Node-B, an eNode B, and a basestation.

As described above, in the following description, a problem which mayoccur when data stored in a message 3 (Msg3) buffer is transmittedaccording to a reception mode of an Uplink (UL) Grant signal will bedescribed in detail and a method of solving the problem will bedescribed. Transmission and reception of a signal using a random accessprocedure and a Hybrid Automatic Repeat Request (HARQ) scheme will bedescribed in detail.

FIG. 4 is a view illustrating an operating procedure of a terminal (UE)and a base station (eNode B) in a non-contention based random accessprocedure.

(1) Random Access Preamble Assignment

As described above, a non-contention based random access procedure maybe performed (1) in a handover procedure and (2) when the random accessprocedure is requested by a command of an eNode B. Even in these cases,a contention based random access procedure may be performed.

First, it is important that a specific random access preamble withoutthe possibility of collision is received from the eNode B, for thenon-contention based random access procedure. Methods of receiving therandom access preamble may include a method using a handover command anda method using a Physical Downlink Control Channel (PDCCH) command. TheUE receives an assigned random access preamble (S401).

(2) Message 1 Transmission

The UE transmits the preamble to the eNode B after receiving theassigned random access preamble from the eNode B as described above(S402).

(3) Message 2 Transmission

The UE attempts to receive a random access response within a randomaccess response reception window indicated by the eNode B through ahandover command or system information after transmitting the randomaccess preamble in step S402 (S403). More specifically, the randomaccess response information may be transmitted in the form of a MediumAccess Control (MAC) Packet Data Unit (PDU), and the MAC PDU may betransferred via a Physical Downlink Shared Channel (PDSCH). In addition,the UE preferably monitors the PDCCH in order to enable to the UE toproperly receive the information transferred via the PDSCH. That is, thePDCCH may preferably include information about a UE that should receivethe PDSCH, frequency and time information of radio resources of thePDSCH, a transfer format of the PDSCH, and the like. Here, if the PDCCHhas been successfully received, the UE may appropriately receive therandom access response transmitted on the PDSCH according to informationof the PDCCH. The random access response may include a random accesspreamble identifier (e.g. Random Access-Radio Network TemporaryIdentifier (RA-RNTI)), an UL Grant indicating uplink radio resources, atemporary C-RNTI, a Time Advance Command (TAC), and the like.

As described above, the reason why the random access response includesthe random access preamble identifier is because a single random accessresponse may include random access response information of at least oneUE and thus it is reported to which UE the UL Grant, the TemporaryC-RNTI and the TAC are valid. In this step, it is assumed that the UEselects a random access preamble identifier matched to the random accesspreamble selected by the UE in step S402.

In the non-contention based random access procedure, it is determinedthat the random access procedure is normally performed, by receiving therandom access response information, and the random access procedure maybe finished.

FIG. 5 is a view illustrating an operating procedure of a UE and aneNode B in a contention based random access procedure.

(1) Message 1 Transmission

First, the UE may randomly select a single random access preamble from aset of random access preambles indicated through system information or ahandover command, and select and transmit a Physical Random AccessChannel (PRACH) capable of transmitting the random access preamble(S501).

(2) Message 2 Reception

A method of receiving random access response information is similar tothe above-described non-contention based random access procedure. Thatis, the UE attempts to receive its own random access response within arandom access response reception window indicated by the eNode B throughthe system information or the handover command, after the random accesspreamble is transmitted in step S501, and receives a Physical DownlinkShared Channel (PDSCH) using random access identifier informationcorresponding thereto (S502). Accordingly, the UE may receive a ULGrant, a Temporary C-RNTI, a TAC and the like.

(3) Message 3 Transmission

If the UE has received the random access response valid for the UE, theUE may process all of the information included in the random accessresponse. That is, the UE applies the TAC, and stores the temporaryC-RNTI. In addition, data which will be transmitted in correspondencewith the reception of the valid random access response may be stored ina Msg3 buffer. A process of storing the data in the Msg3 buffer andtransmitting the data will be described later with reference to FIG. 7.

The UE uses the received UL Grant so as to transmit the data (that is,the message 3) to the eNode B (S503). The message 3 should include a UEidentifier. In the contention based random access procedure, the eNode Bmay not determine which UEs are performing the random access procedure,but later the UEs should be identified for contention resolution.

Here, two different schemes for including the UE identifier may beprovided. A first scheme is to transmit the UE's cell identifier throughan uplink transmission signal corresponding to the UL Grant if the UEhas already received a valid cell identifier allocated by acorresponding cell prior to the random access procedure. Conversely, thesecond scheme is to transmit the UE's unique identifier (e.g., S-TMSI orrandom ID) if the UE has not received a valid cell identifier prior tothe random access procedure. In general, the unique identifier is longerthan the cell identifier. If the UE has transmitted data correspondingto the UL Grant, the UE starts a contention resolution (CR) timer.

(4) Message 4 Reception

After transmitting the data with its identifier through the UL Grantincluded in the random access response, the UE waits for an indication(instruction) from the eNode B for contention resolution. That is, theUE attempts to receive the PDCCH so as to receive a specific message(S504). Here, there are two schemes to receive the PDCCH. As describedabove, the UE attempts to receive the PDCCH using its own cellidentifier if the message 3 transmitted in correspondence with the ULGrant is transmitted using the UE's cell identifier, and the UE attemptsto receive the PDCCH using the temporary C-RNTI included in the randomaccess response if the identifier is its unique identifier. Thereafter,in the former scheme, if the PDCCH is received through its own cellidentifier before the contention resolution timer is expired, the UEdetermines that the random access procedure has been normally performedand completes the random access procedure. In the latter scheme, if thePDCCH is received through the temporary C-RNTI before the contentionresolution timer has expired, the UE checks data transferred by thePDSCH indicated by the PDCCH. If the unique identifier of the UE isincluded in the data, the UE determines that the random access procedurehas been normally performed and completes the random access procedure.

Hereinafter, the LTE system, by way of example, a uplink HybridAutomatic Repeat Request (HARQ) scheme of a MAC layer will be described,concentrating on the transmission of uplink data.

FIG. 6 is a view illustrating an HARQ scheme.

A UE may receive UL Grant information or UL scheduling information froman eNode B on a PDCCH (step S601), in order to transmit data to theeNode B by the HARQ scheme. In general, the UL scheduling informationmay include a UE identifier (e.g., a C-RNTI or a Semi-PersistentScheduling C-RNTI), resource block assignment, transmission parameters(modulation, coding scheme and redundancy version), and a New DataIndicator (NDI). In the LTE system, the UE has eight HARQ processes andthe HARQ processes are synchronously performed with Transmission TimeIntervals (TTIs). That is, specific HARQ processes may be sequentiallyassigned according to points in time when data is received, in a mannerof using the first HARQ process at TTI 9 and using the second HARQprocess at TTI 10 after a first HARQ process is used at TTI 1, a secondHARQ process is used at TTI 2, . . . , and an eighth HARQ process isused at TTI 8.

In addition, since the HARQ processes are synchronously assigned asdescribed above, a HARQ process connected to a TTI in which a PDCCH forinitial transmission of specific data is received is used for thetransmission of the data. For example, if it is assumed that the UE hasreceived a PDCCH including UL scheduling information at an N^(th) TTI,the UE transmits data at an (N+4)^(th) TTI. In other words, a K^(th)HARQ process assigned at the (N+4)^(th) TTI is used for the transmissionof the data. That is, the UE may transmit the data to the eNode B on aPUSCH according to the UL scheduling information after checking the ULscheduling information transmitted to the UE by monitoring the PDCCH atevery TTI (step S602).

When the data has been received, the eNode B stores the data in a softbuffer and attempts to decode the data. The eNode B transmits an ACKsignal if the decoding of the data succeeds and transmits an NACK signalif the decoding of the data fails. An example in which the decoding ofthe data fails and the eNode B transmits the NACK signal on a PhysicalHARQ Indicator Channel (PHICH) is shown in FIG. 6 (step S603).

When the ACK signal has been received from the eNode B, the UEdetermines that the transmission of the data to the eNode B succeeds andtransmits next data. However, when the UE receives the NACK signal asshown in FIG. 6, the UE may determine that the transmission of the datato the eNode B has failed and retransmit the same data by the samescheme or a new scheme (step S604).

The HARQ retransmission of the UE may be performed by a non-adaptivescheme. That is, the initial transmission of specific data may beperformed when the PDCCH including the UL scheduling information shouldbe received, but the retransmission may be performed even when the PDCCHis not received. In the non-adaptive HARQ retransmission, the data isretransmitted using the same UL scheduling information as the initialtransmission at a TTI at which a next HARQ process is assigned, withoutreceiving the PDCCH.

The HARQ retransmission of the UE may be performed by an adaptivescheme. In this case, transmission parameters for retransmission arereceived on the PDCCH, but the UL scheduling information included in thePDCCH may be different from that of the initial transmission accordingto channel statuses. For example, if the channel status is better thanthat of the initial transmission, transmission may be performed at ahigh bit rate. In contrast, if the channel status is worse than that ofthe initial transmission, transmission may be performed at a lower bitrate than that of the initial transmission.

If the UE receives the UL scheduling information on the PDCCH, it isdetermined whether data which should be transmitted at this time is datawhich is initially transmitted or previous data which is retransmitted,by an NDI field included in the PDCCH. The NDI field is toggled in theorder of 0, 1, 0, 1, . . . whenever new data is transmitted as describedabove, and the NDI field of the retransmission has the same value asthat of the initial transmission. Accordingly, the UE may compare theNDI field with the previously transmitted value so as to determinewhether or not the data is retransmitted.

The UE counts the number of times of transmission (CURRENT_TX_NB)whenever data is transmitted by the HARQ scheme, and deletes the datastored in the HARQ buffer when CURRENT_TX_NB has reached a maximumtransmission number set in an RRC layer.

When the retransmitted data is received, the eNode B attempts to combinethe received data and the data stored in the soft buffer due to thefailure of the decoding by various schemes and decodes the combineddata. The eNode B transmits an ACK signal to the UE if the decodingsucceeds and transmits an NACK signal to the UE if the decoding fails.The eNode B repeats a process of transmitting the NACK signal andreceiving the retransmitted data until the decoding of the datasucceeds. In the example of FIG. 6, the eNode B attempts to combine thedata retransmitted in step S604 and the data which is previouslyreceived and stored and decodes the combined data. The eNode B transmitsthe ACK signal to the UE on the PHICH if the decoding of the receiveddata succeeds (step S605). The UE may transmit the UL schedulinginformation for the transmission of next data to the UE on the PDCCH,and may transmit the NDI toggled to 1 in order to report that the ULscheduling information is not used for the adaptive retransmission, butis used for the transmission of new data (step S606). The UE maytransmit new data to the eNode B on the PUSCH corresponding to thereceived UL scheduling information (step S607).

The random access procedure may be triggered in the above-describedcases as described above. Hereinafter, the case where the UE requests ULradio resources will be described.

FIG. 7 is a view illustrating a method of transmitting a message 3 in arandom access procedure when UL radio resources are requested.

When new data is generated in a transfer buffer 601 of the UE, forexample, an RLC buffer and a PDCP buffer, the UE should generally informthe eNode B of information about the generation of the data. Moreaccurately, when data having priority higher than that of data stored inthe transfer buffer of the UE is generated, the UE informs the eNode Bthat the data is generated.

This indicates that the UE requests radio resources to the eNode B inorder to transmit the generated data. The eNode B may assign properradio resources to the UE according to the above information. Theinformation about the generation of the data is called a buffer statusreport (hereinafter, referred to as “BSR”). Hereinafter, as describedabove, the request for the transmission of the BSR is represented bytriggering of the BSR transmission (S6100). If the BSR transmission istriggered, the UE should transmit the BSR to the eNode B. However, ifthe radio resources for transmitting the BSR are not present, the UE maytrigger a random access procedure and attempt to request radio resources(S6200).

As described above, if the random access procedure for requesting theradio resources to the eNode B is triggered, the UE may transmit arandom access preamble to the eNode B and receive a random accessresponse message corresponding thereto as described with reference toFIGS. 4 and 5. In addition, a message 3 (that is, a MAC PDU) including aUE identifier and a BSR may be generated and stored in a Msg3 buffer602, in a MAC layer of the UE through a UL Grant signal included in therandom access response message. The message 3 stored in the Msg3 buffer602 may be copied and stored in a HARQ process buffer 603 indicated bythe UL Grant information. FIG. 7 shows, by way of example, the casewhere the HARQ process A is used for the transmission of the message 3.Thus, the message 3 is copied to the HARQ buffer 603 corresponding tothe HARQ process A. The message 3 stored in the HARQ buffer 603 may betransmitted to the eNode B on a PUSCH.

Meanwhile, if the UE should perform retrial of the random accessprocedure due to contention resolution failure, the UE may transmit therandom access preamble to the eNode B again and receive a random accessresponse (S6300). However, in the retried random access procedure, theUE uses the message 3 stored in the Msg3 buffer 602 again, withoutgenerating a new message 3. That is, the UE may copy and store the MACPDU corresponding to the message 3 stored in the Msg3 buffer 602 in aHARQ buffer 604, and transmit the MAC PDU, according to the UL Grantsignal included in the random access response received in the retriedrandom access procedure. FIG. 7 shows the case where the reattemptedrandom access procedure is performed by a HARQ process B. The datastored in the Msg3 buffer 602 may be copied into the HARQ buffer B andtransmitted.

As described above, if the random access response is received while therandom access procedure is performed, the UE stores the message 3 storedin the Msg3 buffer in the HARQ buffer and transmits the message 3. Asdescribed above, in the current the LTE system standard for the HARQprocess, it is defined that the transmission of the data stored in theMsg3 buffer is triggered by the reception of any UL Grant signal.Accordingly, the CR timer may be erroneously driven such that anerroneous contention resolution process is performed. Due to theerroneous contention resolution procedure, the above-described BSR maynot be normally transmitted and the UE may come to deadlock. Thisproblem will be described in detail with reference to FIG. 8.

FIG. 8 is a view illustrating a problem which may occur when data storedin a Msg3 buffer is transmitted by an Uplink (UL) Grant signal receivedon a message other than a random access response message.

As described with reference to FIG. 7, the UE may trigger the BSR whenhigh priority data is generated, transmit the random access preamble inorder to transmit the BSR to the eNode B (S801), and receive the randomaccess response corresponding thereto (S802).

Thereafter, the UE may transmit a message 3 including the BSR via ULGrant information included in the random access response messagereceived in step S802 (S803). If the message 3 is transmitted, the CRtimer is operated as described with reference to FIG. 5.

If the random access procedure is completed before the CR timer expires,the UE determines that the random access procedure has not beensuccessfully completed (S804). In this case, the UE may try to restartthe random access procedure from the transmission of the random accesspreamble.

At this time, since the eNode B does not yet know that the UE isperforming the random access procedure, the eNode B may transmit a ULGrant signal independent of the random access procedure on a maskedPDCCH (S805). In this case, according to the current LTE systemstandard, the UE transmits the message 3 stored in the Msg3 bufferaccording to the UL Grant signal received on the PDCCH in step S805(S806). In addition, when the message 3 is transmitted, the CR timer isrestarted. That is, even when the UE does not perform the transmissionof the random access preamble and the reception of the random accessresponse message, the CR timer is restarted in step S806.

Although the CR timer is started as the UE transmits the message 3 instep S806, the eNode B may not know that the UE is performing the randomaccess procedure because the reception of the random access preamble andthe transmission of the random access response message are notperformed. If another UL Grant signal is received on the PDCCH includingthe UE identifier (S807), the UE determines that the ongoing randomaccess procedure is successfully completed. Accordingly, the UE may stopthe ongoing CR time (S808).

If the message 3 transmitted to the eNode B in step S806 is notsuccessfully received by the eNode B (A), the UE no longer transmits themessage 3 including the BSR. Accordingly, if additional data is notgenerated, the UE may not transmit the data generated in the transferbuffer to the eNode B.

The above-described problem will be described as follows.

According to the current LTE system standard, if the UL Grant signal isreceived in a state in which the data is stored in the Msg3 buffer, theUE transmits the data stored in the Msg3 buffer to the eNode B. At thistime, the UL Grant signal may be transmitted by the eNode B, not for thetransmission of the data stored in the Msg3 buffer, but for thetransmission of other data. Accordingly, the CR timer may be erroneouslystarted.

In addition, if the eNode B does not know that the CR timer iserroneously started in the UE and transmits the UL Grant signal for thetransmission of other data as described with reference to FIG. 8,information (e.g., BSR) to be transmitted through the message 3 may belost.

In addition, the UE may not receive a message 4 for completing a propercontention resolution procedure even with respect to the ongoing randomaccess procedure.

In a preferred embodiment of the invention for solving theabove-described problem, the data stored in the Msg3 buffer isrestrictively transmitted only in the case where the UL Grant signalreceived from the eNode B is received on the random access responsemessage, but not in all cases where the UL Grant signal is received fromthe eNode B. If the UL Grant signal is received on the masked PDCCH notby the random access response message but by the UE identifier (C-RNTIor a Semi Persistent Scheduling Radio Network Temporary Identifier(SPS-RNTI)) in a state in which the data is stored in the Msg3 buffer, amethod of acquiring and transmitting new data (MAC PDU) to the eNode Binstead of the data stored in the Msg3 buffer is suggested.

FIG. 9 is a flowchart illustrating a method of transmitting UL data by aUE according to a preferred embodiment of the present invention. In moredetail, FIG. 9 shows the operation of a HARQ entity of the UE accordingto an embodiment of the present invention at every TTI.

First, the HARQ entity of the UE may identify a HARQ process associatedwith a TTI (S901). If the HARQ process associated with the TTI isidentified, the HARQ entity of the UE may determine whether or not a ULGrant signal received from the eNode B indicated at the TTI (S902). TheUE may determine whether or not a HARQ buffer corresponding to the HARQprocess is empty if there is no information about the received UL Grantsignal at the TTI, and perform non-adaptive retransmission as describedwith reference to FIG. 6 if there is data in the HARQ buffer (S903).

Meanwhile, if there is a UL Grant signal received from the eNode B atthe TTI, it may be determined (1) whether the UL Grant signal is notreceived on the PDCCH indicated by the temporary C-RNTI and the NDI istoggled from the value during transmission prior to the HARQ process,(2) whether there is previous NDI and this transmission is initialtransmission of the HARQ process, (3) whether the UL Grant signal isreceived on the PDCCH indicated by the C-RNTI and the HARQ buffer of theHARQ process is empty, or (4) whether the UL Grant signal is received onthe random access response message (S904). If any one of the conditions(1) to (4) is satisfied in step S904 (A), the method progresses to stepS906. In contrast, if any one of the conditions (1) to (4) is notsatisfied in step S904 (B), the method progresses to step S905 ofperforming adaptive retransmission using the UL Grant signal (S905).

Meanwhile, the UE determines whether there is data in the Msg3 buffer instep S906 (S906). In addition, even when there is data in the Msg3buffer, the UE determines whether the received UL Grant signal isreceived on the random access response message (S907). That is, the UEaccording to the present embodiment transmits the data stored in theMsg3 buffer only when there is data in the Msg3 buffer when receivingthe UL Grant signal and the UL Grant signal is received on the randomaccess response message (S908). If there is no data in the Msg3 bufferwhen receiving the UL Grant signal or the UL Grant is not received onthe random access response message, the UE determines that the eNode Bmakes a request not for the transmission of the data stored in the Msg3buffer but for transmission of new data, and performs new datatransmission (S909). In more detail, the HARQ entity of the UE may becontrolled such that a MAC PDU including new data from a multiplexingand assembly entity is acquired and is transmitted through the HARQprocess.

Hereinafter, an example applied to a process of transmitting a BSR bythe UE which operates by the embodiment described with reference to FIG.9 as shown in FIG. 8 will be described.

FIG. 10 is a view illustrating a method of transmitting UL data when aBSR is triggered in a UE, according to an embodiment of the presentinvention.

As described above, new data may be generated in the RLC and PDCPbuffers of the UE. It is assumed that the generated new data has higherpriority than that of the data already stored in the RLC and PDCPbuffers. The UE may trigger the BSR transmission in order to inform aneNode B of information about the generation of the data (step 1).

The UE should transmit the BSR according to BSR transmission trigger,but, in a special case, there may be no radio resource for transmittingthe BSR. In this case, the UE may trigger a random access procedure fortransmitting the BSR. It is assumed that the random access proceduretriggered in the present embodiment is the contention based randomaccess procedure described with reference to FIG. 5.

The UE may transmit a random access preamble to the eNode B according tothe triggering of the random access procedure (step 2).

The eNode B may receive the random access preamble transmitted by the UEand transmit a random access response message to the UE (step 3). The UEmay receive the random access response message.

The UE may generate a message 3 including the BSR and a UE identifieraccording to a UL Grant signal included in the random access responsemessage received in step 3 and store the message 3 in a Msg3 buffer(step 4).

The UE may select a HARQ process according to the UL Grant informationincluded in the random access response message received in step 3 andcopy and store the message 3 stored in the Msg3 buffer in the buffercorresponding to the selected HARQ process. Thereafter, the data storedin the HARQ buffer may be transmitted to the eNode B according to the ULHARQ procedure described with reference to FIG. 6 (step 5). The UEstarts (or restarts) the CR timer by the transmission of the message 3.

When the CR timer expires, the UE may perform retrial of the randomaccess procedure. That is, a random access preamble and a PRACH resourcemay be prepared to be selected and transmitted to the eNode B. However,in a state in which the CR timer is not operated, the UE may receive theUL Grant signal from the eNode B on a PDCCH masked by a UE identifier(step 6).

When the UL Grant signal has been received on the PDCCH in step 6, theUE generates new data different from the data stored in the Msg3 bufferaccording to the UL Grant information received in step 6 as a new MACPDU, unlike the procedure of the embodiment of FIG. 8 for transmittingthe message 3 stored in the Msg3 buffer according to the UL Grantinformation received in step 6 (step 7). In more detail, if the UEreceives the UL Grant signal in step 6 but does not receive the UL Grantsignal on the random access response message, a MAC PDU for transmittingnot the data stored in the Msg3 buffer but new data from a multiplexingand assembly entity may be acquired and transmitted using a HARQ processcorresponding thereto.

After the new MAC PDU is generated, the UE according to the presentembodiment may select a HARQ process according to the UL Grant signalreceived in step 6, store the MAC PDU newly generated in step 7 in thebuffer corresponding to the HARQ process, and transmit the MAC PDU tothe eNode B according to the UL HARQ procedure (step 8).

Thereafter, the UE may perform a random access procedure including thetransmission of the random access preamble and the reception of therandom access response and transmit the BSR stored in the Msg3 buffer tothe eNode B.

According to the above-described embodiment, it is possible to preventthe eNode B from erroneously operating the CR timer due to the UL Grantsignal transmitted not for transmission of the data stored in the Msg3buffer but for transmission of new data. Accordingly, the problem thatthe message 3 is lost may be solved. In addition, the random accessprocedure of the UE with the eNode B may be normally performed.

Unlike the above-described embodiment, as another embodiment of thepresent invention, a method of performing a process while ignoring theUL Grant signal if the UL Grant signal is received from the eNode B onthe PDCCH masked by the UE identifier during the random access procedureof the UE may be implemented. In this case, the UE may transfer themessage 3 to the eNode B by the normal random access procedure, and theeNode B may retransmit the UL Grant signal for the transmission of newdata after the random access procedure of the UE is completed.

Hereinafter, the configuration of the UE for implementing theabove-described embodiment of the present invention will be described.

FIG. 11 is a schematic view showing the configuration of a UE accordingto an embodiment of the present invention.

As shown in FIG. 11, the UE according to the present embodiment mayinclude a reception (Rx) module 1101 for receiving a UL Grant signalfrom an eNode B on a specific message, a transmission (TX) module 1102for transmitting data to the eNode B using the received UL Grant signal,a Msg3 buffer 1103 for storing UL data transmitted in a random accessprocedure, and a HARQ entity 1104 for controlling the transmission of ULdata of the UE.

In particular, the HARQ entity 1104 of the UE according to the presentembodiment performs a function of determining whether there is datastored in the Msg3 buffer 1103 when the Rx module 1101 receives the ULGrant signal and a function of determining whether the Rx module 1101receives the UL Grant signal on a random access response message. Ifthere is data stored in the Msg3 buffer 1103 when the Rx module 1101receives the UL Grant signal and the RX module 1101 receives the ULGrant signal on the random access response message, the data stored inthe Msg3 buffer 1103 is controlled to be acquired and transmitted to theeNode B. If there is no data stored in the Msg3 buffer 1103 when the Rxmodule 1101 receives the UL Grant signal and the RX module 1101 receivesthe UL Grant signal not on the random access response message but on thePDCCH, the data stored in the Msg3 buffer 1103 is not transmitted butnew data is acquired from the multiplexing and assembly entity in theform of a MAC PDU and is transmitted to the eNode B.

In addition, in order to perform the UL HARQ procedure, the UE accordingto the present embodiment may include one or more HARQ processes 1106and HARQ buffers 1107 corresponding to the HARQ processes 1106. In thecurrent LTE system, eight independent HARQ processes are defined foruse, but the present invention is not limited thereto.

Meanwhile, the HARQ entity 1104 according to the present embodiment maytransfer the data acquired from the multiplexing and assembly entity1105 or the msg3 buffer 1103 to a specific HARQ process 1106 using theabove-described configuration, and control the specific HARQ process1106 to transmit the data acquired from the multiplexing and assemblyentity 1105 or the Msg3 buffer 1103 through the Tx module 1102. Asdescribed above, if the specific HARQ process 1106 transmits the datastored in the Msg3 buffer 1103 through the Tx module 1102 as describedabove, the data stored in the Msg3 buffer 1103 may be copied into thespecific HARQ buffer 1107 corresponding to the specific HARQ process1106 and the data copied into the specific HARQ buffer 1107 may betransmitted through the Tx module 1102.

At this time, the data stored in the Msg3 buffer 1103 is a MAC PDUincluding a UE identifier and may further include information such as aBSR according to the purpose of the random access procedure.

In the configuration of the UE shown in FIG. 11, the Tx module 1102 andthe Rx module 1101 may be configured as a physical layer processingmodule 1108, and the HARQ entity 1104, the multiplexing and assemblyentity 1105 and one or more HARQ processes 1106 may be configured as aMAC layer module 1109. However, the invention is not limited thereto. Inaddition, the Msg3 buffer 1103 and the HARQ buffers 1107 correspondingto the HARQ processes 1106 may be implemented using any storage medium.

Although the signal transmission or reception technology and the UE forthe same are applied to a 3GPP LTE system, they are applicable tovarious mobile communication systems having a similar procedure, inaddition to the 3GPP LTE system.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of transmitting data by a user equipment through an uplink,the method comprising: receiving an uplink grant (UL Grant) signal froma base station on a specific message; determining whether there is datastored in a message 3 (Msg3) buffer when receiving the UL Grant signalon the specific message; determining whether the specific message is arandom access response message; and transmitting the data stored in theMsg3 buffer to the base station using the UL Grant signal received onthe specific message, if there is data stored in the Msg3 buffer whenreceiving the UL Grant signal on the specific message and the specificmessage is the random access response message.
 2. The method accordingto claim 1, further comprising: transmitting new data to the basestation in correspondence with the UL Grant signal received on thespecific message, if there is no data stored in the Msg3 buffer whenreceiving the UL Grant signal on the specific message or the specificmessage is not the random access response message.
 3. The methodaccording to claim 2, wherein the transmitting the new data to the basestation includes: acquiring a Medium Access Control Protocol Data Unit(MAC PDU) from a multiplexing and assembly entity; and transmitting theMAC PDU to the base station.
 4. The method according to claim 2, whereinthe UL Grant signal received on the specific message is a UL Grantsignal received on a Physical Downlink Control Channel (PDCCH), andwherein the user equipment transmits new data in correspondence with theUL Grant signal received on the PDCCH.
 5. The method according to claim1, wherein the data stored in the Msg3 buffer is a Medium Access ControlProtocol Data Unit (MAC PDU) including a user equipment identifier. 6.The method according to claim 5, wherein the data stored in the Msg3buffer further includes information about a buffer status report (BSR)if the user equipment starts a random access procedure for the BSR.
 7. Auser equipment comprising: a reception module receiving an uplink grant(UL Grant) signal from a base station on a specific message; atransmission module transmitting data to the base station using the ULGrant signal received on the specific message; a message 3 (Msg3) bufferstoring UL data to be transmitted in a random access procedure; and aHybrid Automatic Repeat Request (HARQ) entity determining whether thereis data stored in the Msg3 buffer when the reception module receives theUL Grant signal and the specific message is a random access responsemessage, acquiring the data stored in the Msg3 buffer if there is datastored in the Msg3 buffer when the reception module receives the ULGrant signal and the specific message is the random access responsemessage, and controlling the transmission module to transmit the datastored in the Msg3 buffer to the base station using the UL Grant signalreceived by the reception module on the specific message.
 8. The userequipment according to claim 7, further comprising a multiplexing andassembly entity used for transmission of new data, wherein the HARQentity acquires the new data to be transmitted from the multiplexing andassembly entity if there is no data stored in the Msg3 buffer when thereception module receives the UL Grant signal on the specific message orthe received message is not the random access response message, andcontrols the transmission module to transmit the new data acquired fromthe multiplexing and assembly entity using the UL Grant signal receivedby the reception module on the specific message.
 9. The user equipmentaccording to claim 8, further comprising: one or more HARQ processes;and HARQ buffers respectively corresponding to the one or more HARQprocesses, wherein the HARQ entity transfers the data acquired from themultiplexing and assembly entity or the Msg3 buffer to a specific HARQprocess of the one or more HARQ processes and controls the specific HARQprocess to transmit the data acquired from the multiplexing and assemblyentity or the Msg3 buffer through the transmission module.
 10. The userequipment according to claim 9, wherein, when the specific HARQ processtransmits the data stored in the Msg3 buffer through the transmissionmodule, the data stored in the Msg3 buffer is controlled to be copiedinto a specific HARQ buffer corresponding to the specific HARQ process,and the data copied into the specific HARQ buffer is controlled to betransmitted through the transmission module.
 11. The user equipmentaccording to claim 8, wherein the UL Grant signal received by thereception module on the specific message is a UL Grant signal receivedon a Physical Downlink Control Channel (PDCCH), and wherein the HARQentity controls new data to be transmitted in correspondence with thereceived UL Grant signal received on the PDCCH.
 12. The user equipmentaccording to claim 7, wherein the UL Grant signal received by thereception module on the specific message is a UL Grant signal receivedon a random access response message received on Physical Downlink SharedChannel (PDSCH), and wherein the HARQ entity controls the data stored inthe Msg3 buffer to be transmitted using the UL Grant signal received onthe random access response message if there is data stored in the Msg3buffer when the reception module receives the UL Grant signal on therandom access response message.
 13. The user equipment according toclaim 7, wherein the data stored in the Msg3 buffer is a Medium AccessControl Protocol Data Unit (MAC PDU) including a user equipmentidentifier.